This is a competitive renewal of NIH T32 HL-07910 entitled: Basic Science Studies on Gene Therapy of Blood Diseases which is currently in its 15th year of funding. The discipline of gene therapy has had its ups and downs, but to continue to advance the field, we must train the next generation of investigators in this area. The aim of this program is to continue to train this next generation of scientists in the clinically-relevant medical area of gene transfer for effective modulation of normal and abnormal cell growth and for gene therapy to correct blood diseases. We request 4 pre- and 5 post-doctoral slots, an increase of 1 pre-doc slot. We have an outstanding group of 23 very productive, interactive, and well-respected investigators as mentors with their primary and/or secondary faculty appointments in 8 departments of the medical school. These mentors have over their career trained a total of 169 pre-doctoral PhD and 284 post-doctoral students. Since the competitive renewal of this program in 2009, we were able to train and/or are in the process of training 11 pre- and 13 post-doctoral students, who have published 112 papers [37 (Pre-Doc) and 75 (Post-Doc)]. The Program Director (PD) has trained 17 pre-doctoral and 55 post- doctoral/clinical fellows, has published over 720 papers and been continuously funded by the NIH since 1978. He is a recognized authority on hematopoietic stem and progenitor cells, the regulation of hematopoiesis, and has had his work translated into clinical utility. The Co-PD, is also a well-recognized and well-funded productive investigator who has trained numerous students and fellows, and has had his work translated for clinical benefit. The PD and Co-PD have extensive administrative experience and have worked for many years in the area of gene transfer in efforts to enhance approaches to gene therapy. The vast majority of our trainees, since initial funding of this grant in 1999, have gone on to careers in academia and other research intensive areas of employment. Training of our pre- and post-doctoral students entails one-on-one interactions, committee and group mentorship, lab meetings, special seminars in the area of this training program, didactic courses, ethical training, presentations at scientific meetings and high expectations for the trainees to publish in respected scientific and medical journals, and to continue in their career development leading them to become productive independent investigators whose work will benefit healthcare in general and gene transfer/gene therapy in specific. Our training efforts are monitored and enhanced by both internal and external advisory committees.